1、第三课时 Section A Grammar Focus单元语法精讲精练be supposed to do sth.中的to是动词不定式符号，其后要跟动词原形；be动词随主语的人称、数和时态的变化而变化。1be supposed to do sth.意为“应该做某事”，它可以表示劝告、建议、义务、责任等，相当于情态动词should。如：Everyone is supposed to wear a seat belt in a car.每个人在坐车时都应该系安全带。2其否定形式为：be not supposed to do sth.，常用于口语中，意为“不被许可/不应该做某事”。如：You ar
2、e not supposed to smoke on the bus.你不应该在公交车上抽烟。3其一般疑问句形式为：Be主语supposed to do其他？如：Was Lucy supposed to lock the door when she left the classroom?当露西离开教室时，她应该锁门吗？4其特殊疑问句形式为：特殊疑问词be主语supposed to do其他？如：What are we supposed to do to save water in our daily life?在日常生活中，我们应该做什么来节约用水？5was/were supposed to
3、do sth.相当于should have done sth.表示过去本应该做某事而并没有做。如：The train was supposed to arrive half an hour ago.火车本该在半小时之前到达。be expected to意为“被期望”，表示一种可能性。其中to是动词不定式符号，其后要接动词原形。be动词有人称和时态的变化，其否定形式要在be动词后加not。如：She is expected to be a good doctor.她有望成为一名好医生。“It isadj.to do sth.”为固定句型，其中it是形式主语，真正的主语是动词不定式(短语)。因为动
4、词不定式(短语)作主语相对较长，为了避免头重脚轻，所以用it作形式主语。【拓展】(1)“It isadj.for sb.to do sth.”意为“对某人来说做某事是的”。此句型中的形容词常用于表示事物的特征、特点，如easy，impossible，difficult，interesting，important，hard等，用来说明后面的动词不定式(短语)。如：Its hard for me to answer your question.我很难回答你的问题。(2)“It isadj.of sb.to do sth.”意为“做某事某人是的”。此句型中的形容词常用于表示人物的性格、品德，如goo
5、d，kind，nice，clever，polite等，用来说明of后的sb.。如：Its very kind of you to help me with my English.你帮助我学习英语真是太好了。一、单项选择。()1.Parents are _ to teach their children how to develop a good habit.Ataught BallowedCsupported Dsupposed()2.Students are not supposed _ loudly in the reading room.Aspeak BspeakingCto speak
6、 Dspoke()3.She _ to clean the tables after dinner，but she forgot it.Ais supposing Bis supposedCwas supposing Dwas supposedDCD()4.We are supposed _ with some housework at home when we have free time.Ato help Bhelping Chelped Dhelp()5.If you are invited to dinner by Western friends，you will _ to stay
7、and talk around the table until the last dish is served.Aexpect BexpectedCbe expecting Dbe expectedAD()6.You are expected _ a diary in English every day if you want to improve your writing skills.Akeep BkeptCkeeping Dto keep()7.Its difficult _ me to finish the math problems alone，so its kind _ you t
8、o help me.(易错题)Aof；of Bfor；ofCof；for Dfor；for()8.Its important for us _ a healthy lifestyle.Ato have Bhave Chaving DhadDBA()9.Is it necessary _ us _ no to plastic straws(塑料吸管)?Yes，it is.We can protect the environment if we do so.(原创题)Aof；saying Bfor；sayingCfor；to say Dof；to say()10.It is wise _ Lind
9、a to make up her mind _ to play an instrument.A.for；learning Bfor；to learnCof；learning Dof；to learnCD二、按要求完成下列句子。11He is supposed to be an expert in this field.(改为否定句)He _ _ _ to be an expert in this field.12Mary is supposed to wear a dress.(改为一般疑问句)_ Mary _ _ wear a dress?13To hand in our homework
10、on time is necessary.(改为同义句)_ _ _ _ _ our homework on time.14They are supposed to get there before five oclock(对画线部分提问)_ _ they _ to get there?15Students are supposed to greet the teachers when classes begin.(对画线部分提问)_ _ students supposed _ _ when classes begin?isnotsupposedIssupposedtoItsnecessaryt
11、ohandinWhenaresupposedWhataretodo三、句子翻译。16我们应该为聚会带一些食物吗？_ _ _ _ bring any food for the party?17期望你更努力地学习。You _ _ _ study harder.18在校期间，中国孩子多学一门语言是非常重要的。(2022，荆州改编)For Chinese children，_ _ _ _ _ a second language in school.19人们不应该在这里抽烟。_20Its difficult for me to learn chemistry well._ArewesupposedtoareexpectedtoitsveryimportanttolearnPeople are not supposed to smoke here.对我来说，学好化学很困难。